There is an increasing demand for deadbolt locks for all types of doors, but the typical lock having a deadbolt and which can be opened with a key from the outside has become quite expensive. They are particularly costly when bought in large numbers for apartments, for example.
One of the problems with apartment house locks is that the tenants move out and frequently take keys with them. This destroys the security of the locks which the keys fit, and requires for a typical tumbler lock, that the apartment house owner, or the tenant, call a locksmith to change the tumblers and provide new keys. This also is very expensive.